"(1) For the purpose of securing that adequate guidance is given to drivers of motor vehicles as to whether any, and if so what, limit of speed is to be observed on any road, it shall be the duty of the Secretary of State in the case of a road for which he is the traffic authority, to erect and maintain the prescribed traffic signs in such positions as may be requisite for that purpose. (2) In the case of any other road it is the duty of the local traffic authority- (a) to erect and maintain the prescribed traffic signs in such positions as may be requisite in order to give effect to general or other directions given by the Secretary of State for the purpose mentioned in subsection (1) above, and (b) to alter or remove traffic signs as may be requisite in order to give effect to such directions, either in consequence of the making of an order by the Secretary of State or otherwise. ... (4) Where no such system of street or carriageway lighting as is mentioned in section 82(1) is provided on a road, but a limit of speed is to be observed on the road, a person shall not be convicted of driving a motor vehicle on the road at a speed exceeding the limit unless the limit is indicated by means of such traffic signs as are mentioned in subsection (1) or subsection (2) above."
"Diagram 670 terminal signing shall be erected on each side of a carriageway at the entry point to a speed restriction to which the sign can be applied."
"Subject to the provisions of these Regulations, a sign for conveying information or a warning, requirement, restriction, prohibition or speed limit of the description specified under a diagram in Schedules 1 to 7, part II of schedule 10 and schedule 12 to traffic on roads shall be of the size, colour and type shown in the diagram."
"for the purposes of this subsection illumination, whether by lighting or by the use of reflectors or reflecting material, or the absence of such illumination, shall be part of the type or character of a sign."
"42-(1) The back of any sign shown in a diagram in Schedules 1 to 5,7, Part 11 of Schedule 10 or in Schedule 12, or prescribed by regulation 53, other than the sign shown in diagram 651,970 971, 972 973.2, 973.3, 2610, 2610.1, 2610.2, 7101.1, 7102,7103,7104 or 7105 shall be coloured- (a) black if the sign is mounted on the same post as that on which light signals prescribed by regulation 33(1)(or those signals as varied in accordance with regulation 34) or light signals prescribed by regulation 33(2) and regulation 35 are mounted; or (b) grey, black or in a non-reflective metallic finish in any other case ... (2) Paragraph (1) shall apply to the back of any backing board or other fitting provided for the assembly of such a sign as is referred to in paragraph (1)(including any container enclosing apparatus for the illumination of such a sign). ... (5) The front of any backing board for a sign mounted otherwise than as described in paragraph (1)(a) shall be coloured either grey or yellow. (6) A yellow backing board for a sign (except one for the sign shown in diagram 2402.1) shall be rectangular in shape. ... (9) In this direction 'backing board' in relation to a sign includes any background (except a wall to which the sign is affixed) against which the sign is displayed."
"(9) In this direction 'backing board' in relation to a sign includes any background (except a wall to which the sign is affixed) against which the sign is displayed."
"To improve conspicuity against a complex or dark background, a sign may be mounted on either a grey or a yellow backing board (direction 42(5)). This board must not be provided with an additional black border."